1. Field of the Invention
This invention relates to the art of webs of record members and to methods of and apparatus for making same.
2. Brief Description of the Prior Art
U.S. Pat. No. 4,002,279 to Klein discloses that notches in webs can be used to control registration in a printer. A major disadvantage of this approach resides in the need to remove and discard small plugs of material, known as xe2x80x9cchadxe2x80x9d during manufacture of such webs. In addition, when the web is a composite pressure sensitive label web, adhesive can to adhere to punches and dies, further complicating the manufacturing process.
U.S. Pat. No. 3,800,701 to Martin shows lateral feed slits or cuts in the carrier web of a composite label web which can coincide or be aligned with butt cuts in the label material. A xe2x80x9cbutt cutxe2x80x9d is an essentially complete line of severing through the label material web but not into the carrier web. However, such feed slits that understandably are made with knives sharp enough to make good feed slits but these feed slits do not produce a through crack in the carrier web, or crush the carrier web to the extent, to allow for reliable detection of light therethrough.
U.S. Pat. No. 4,274,661 to Jenkins shows that feed slits can be made in the carrier web and these feed slits allow one or more flaps to be displaced from the plane of the carrier web.
The invention pertains to a web of record members with an improved arrangement by which the position of the web can be optically detected for registration purposes.
More specifically, it is a feature of the invention to provide an improved web of record members that is easy-to-manufacture, is low in cost, does not remove chad from or displace a portion of the web from the plane of the web, and which can be used to detect reliably the position of the web for registration purposes.
In accordance with specific embodiments of the invention, a web of record members is provided with a series of optically detectable crushed areas and preferably having cracks or fissures disposed at equally longitudinally spaced intervals. It is preferred that the cracks be made by crushing. In one embodiment of the invention, the crushing produces lateral cracks or fissures occurring in the record material web. These crushed areas or cracks or fissures allow enough light to pass through the web to enable reliable detection.
It is preferred that when applying the invention to a composite label web the cracks in the carrier web be made at the butt cuts. In this way an integral butt cutter and crushing element can simultaneously make a butt cut and a crushed area. There is resultant exact registration between the butt cuts and the crushed areas or cracks so that there is exact registration between the labels and the crushed areas or cracks.
The invention is also applicable to webs of tag stock and to linerless pressure sensitive label webs. In such uses the tool comprises a roll with one or more crushing elements and a cooperable back-up roll. The crush element makes a crushed area and preferably a crack or fissure in the web each time it cooperates with the back-up roll so that registration crushed areas or preferably cracks are formed at regular, equally spaced apart intervals. The crush area or cracks allow enough light to pass through the web so that the web can be used for registration purposes.
It is preferred to provide a one-piece tool for making the butt cut and for crushing the carrier web to provide each detectable crushed area or crack.
It is preferred to provide a one-piece rotatory tool for crushing the carrier web to provide each crushed area or crack.
It is preferred to provide an apparatus including a pair of cooperating rolls between which the web of record members can be passed. One of these rolls has a crushing element which crushes the web locally at equally longitudinally spaced intervals to make optically detectable crushed areas or cracks in the web.
In order to detect a crack or fissure forming an optically detectable indicium, a source of light and an optical detector are employed. In the illustrated embodiment, the optical detector is positioned relative to the source of light to detect light impinging on the detector and the detector is spaced from the source of light to allow the web of record members with the crack or fissure to pass therebetween. The optical detector generates a first output signal representing an amount of light impinging on a first portion of the detector and a second output signal presenting an amount of light impinging on a second portion of the optical detector. A difference circuit is responsive to the first and second output signals to produce a signal that represents the difference therebetween. The difference signal is compared to a reference signal in order to identify an edge of the crack or fissure. The leading and trailing edges of a crack or fissure are thus detectable for accurate registration of the record members with respect to a printhead for printing thereon. There is a predetermined relationship between the crack or fissure and the related label or tag. The label or tag is a top of form position when the printing cycle begins and the top of form position is determined by detection of a crack or fissure (indicium) by the detector at the end of the next previous printing cycle.